Segment Information (Details 1) (USD $) In Millions	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	$ 4,710	$ 4,677	$ 14,202	$ 14,076
Net investment income (loss):
Securities available-for-sale and other	1,062	1,073	3,274	3,275
Equity securities, trading	(1,890)	1,043	(1,684)	(905)
Total net investment income	(828)	2,116	1,590	2,370
Net realized capital losses	575	(257)	241	(522)
Other revenues	63	66	188	195
Total revenues	4,520	6,602	16,221	16,119
Property & Casualty Commercial [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	1,553	1,439	4,568	4,278
Workers' Compensation [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	721	605	2,071	1,754
Property [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	129	137	398	412
Automobiles Commercial [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	146	149	437	453
Package Business [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	289	281	857	842
Liability [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	135	129	404	405
Fidelity and Surety [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	55	56	164	169
Professional Liability [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	78	82	237	243
Group Benefits [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	1,016	1,058	3,136	3,234
Group Disability [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	467	487	1,460	1,520
Group Life and Accident [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	501	513	1,529	1,539
Other Group Benefit [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	48	58	147	175
Consumer Markets [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	930	985	2,825	2,976
Automobiles Consumer [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	649	698	1,978	2,122
Homeowners [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	281	287	847	854
Global Annuity [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	624	657	1,919	1,925
Variable Global Annuity [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	600	629	1,870	1,855
Fixed / MVA and other annuity [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	29	24	56	49
Institutional investment products [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	(5)	4	(7)	21
Life Insurance [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	286	243	796	762
Variable Life Insurance [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	122	113	304	315
Universal Life Insurance [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	109	72	324	282
Term / other life [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	13	12	37	36
PPLI [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	42	46	131	129
Retirement Plans [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	93	89	291	265
401(k) [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	82	77	254	233
Government Plans [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	11	12	37	32
Mutual Funds [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	153	159	506	493
Non-proprietary [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	138	144	461	447
Proprietary [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	15	15	45	46
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Earned premiums, fees and other considerations	$ 55	$ 47	$ 161	$ 143

Net investment income earned on Equity Securities, Trading.

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Net investment income earned on Securities Available-For-Sale and Other, excluding Equity Securities, Trading.

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The income earned from investments in securities and property, equipment and other capital assets. It includes rent from property and equipment, dividends from shares in corporations, and interest from bonds, loans, mortgages, derivatives, commercial paper, bank accounts, certificates of deposits, treasuries, and other financial securities. It does not include realized gains and losses on investments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 16

-Article 12

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 2

-Article 7

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.2)

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Reflects the sum of all other revenue and income recognized by the entity in the period not otherwise specified in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 7

-Section 04

-Paragraph 4

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.4)

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The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 3

-Subparagraph a

-Article 7

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.3(a))

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 325

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6485959&loc=d3e22529-158502

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Aggregate revenue recognized during the period (derived from goods sold, services rendered, insurance premiums, or other activities that constitute an entity's earning process). For financial services companies, also includes investment and interest income, and sales and trading gains.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 5

-Section 03

-Paragraph 1

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of total revenue for the reportable segments, including revenue from external customers, transactions with other operating segments of the same entity, and (gross) interest revenue. All considered to be "operating revenue" for purposes of the taxonomy.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 131

-Paragraph 27

-Subparagraph a, b, c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 280

-SubTopic 10

-Section 50

-Paragraph 22

-Subparagraph (a),(b),(c)

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